Handling of liquid specimens, reagents, and possibly other process fluids is important for the implementation of automated testing methods. Conventionally, liquid specimens, process fluids (e.g., purified water), and liquid reagents are aspirated and/or dispensed within an automated clinical analyzer by using a pipette (sometimes referred to as a “probe”). In certain automated clinical analyzers used to test for the presence of an analyte in a specimen, it may be desirable to precisely aspirate and dispense one or more of the liquids. For example, in some automated clinical analyzers, a portion of a specimen contained in a sample container (such as a test tube, sample cup, vial, or the like) may be aspirated and then transferred into a reaction vessel (e.g., a cuvette) in order to determine a presence of a particular analyte contained therein. As part of this testing process, one or more liquid reagents may be precisely metered into the reaction vessel along with the specimen. In some instances, a dilutant, such as purified water, may be added.
Conventional aspiration systems in such automated clinical analyzers include pipette configurations used for aspirating and dispensing that include a relatively small outer diameter and a small internal passage. The pipette may be coupled to a section of tubing that is, in turn, coupled to one or more pumps (e.g., a piston pump and/or peristaltic pump). The aspiration system, including the pipette and the one or more pumps, is typically primed with purified water known as “liquid backing.” The liquid backing, which may be purified water, acts as the vehicle enabling the aspirating and dispensing of the specimen and/or reagent.
After dispense of a specimen or reagent, it is desirable to clean the pipette properly to avoid carryover of any material (e.g., proteins, reagent, or the like) to subsequently conducted tests. Carryover may affect subsequent test results, and, thus, is generally unwanted. Specimen carryover has been addressed in some instances by using disposable tips on the pipette, which may be disposed after a single specimen dispense. Although this method may mitigate carryover, it adds the cost of the disposable tip, the extra process time to install and dispense of the tip, and the housing size must be increased to accommodate an inventory amount of replacement tips.
In some smaller automated clinical analyzers, wash treatments are used to clean the pipette between dispenses of specimen. In such automated clinical analyzers, a volume of liquid backing may be dispensed into a waste station located in the automated clinical analyzer, which may be used to initially clean the internal passage as well as the outside of the pipette. Some analyzers may also include aspirating and dispensing of a bleach solution as part of the cleaning method. Such bleach solution cleaning may follow the specimen dispense. Bleach solution may be provided in an ancillary bleach pack, and may be dispensed to the waste station after its aspiration. However, in many small automated clinical analyzers, space is at a premium. Further, constant reloading of consumable bleach packs may impact process efficiency as well as overall operating costs. In particular, as the consumable bleach pack is drawn down, the depth of bleach solution available to disinfect the outside of the pipette is reduced. At some depth level, other than empty, the consumable bleach pack may be replaced with a full consumable bleach pack to ensure that the pipette is exposed to bleach of a sufficient depth to minimize carryover of residue from the outside of the pipette.
Accordingly, cleaning methods and apparatus that may mitigate carryover, and/or that may reduce an amount of consumable packs that are used, are desired.